Stabilized aminobenzotrifluorides

ABSTRACT

Without added stabilizers, aminobenzotrifluorides have low thermal and storage stability. 
     The present invention relates to preparations of a stabilized amionbenzotrifluoride, composed essentially of 
     a) an aminobenzotrifluoride of the formula (I), ##STR1## in which R 1  and R 2 , independently of each other, are hydrogen, C 1  -C 6  -alkyl, C 2  -C 6  -alkenyl, substituted or unsubstituted aryl, halogen, CF 3 , nitro, amino, methoxy, hydroxyl or NR 3  R 4 , where R 3  and R 4 , independently of each other, are hydrogen or C 1  -C 5  -alkyl radicals, and the NH 2  group can be located in the 2-, 3- or 4-position in relation to the CF 3  group, and 
     b) at least one base.

Aminobenzotrifluorides are of great industrial importance as startingmaterials for the preparation of numerous relevant compounds, forexample in the fields of plant protective agents and pharmaceuticals.

Aminobenzotrifluorides have low thermal and storage stability. R. G.Jones, J. Amer. Chem. Soc. 69, 2346 (1947) reported that 2- and4-aminobenzotrifluorides change into glass-like polymers on heating.

2-Aminobenzotrifluoride resinifies at 140° to 150° C. in less than 2hours. 4-Aminobenzotrifluoride is no longer stable even at 120° C., andresinifies within 1.5 hours. While chlorine substituents on the ring doincrease the stability, even in this case resinification sets in atabout 180° C. This property impedes the purification of these compounds,for example by distillation, substantially, since the boiling points,even under reduced pressure, are very close to the decompositiontemperature. The distillates are often more unstable than the crudeproducts. In the case of the storage of these compounds, too, forexample as melts, precautions must be taken against overheating,especially since resinification takes place exothermically.

The object on which the present invention was based was therefore tomake available aminobenzotrifluorides in a stabilized form, in whichthey no longer suffer from the disadvantages described above.

It has been found, surprisingly, that aminobenzotrifluorides can bestabilized against thermal decomposition and resinification if a basiccompound is added to them.

The present invention relates to preparations of a stabilizedaminobenzotrifluoride, composed essentially of

a) an aminobenzotrifluoride of the formula (I), ##STR2## in which R¹ andR², independently of each other, are hydrogen, C_(1-C) ₆ -alkyl,preferably C₁ -C₄ -alkyl, in particular methyl; C₂ -C₆ -alkenyl,preferably C₂ -C₄ -alkenyl; substituted or unsubstituted aryl,preferably unsubstituted or substituted phenyl, in particular phenyl,hydroxyphenyl, tolyl, xylyl, aminophenyl, halophenyl and nitrophenyl;halogen, preferably fluorine, chlorine or bromine; CF₃, nitro, amino,methoxy, hydroxyl or --NR³ R⁴, where R³ and R⁴, independently of eachother, are hydrogen or C₁ -C₅ -alkyl radicals, preferably hydrogen or C₁-C₃ -alkyl radicals, and the NH₂ group can be located in the 2-, 3- or4-position in relation to the CF₃ group, and

b) at least one base.

Bases which are preferably employed according to the invention areprimary, secondary or tertiary aliphatic or araliphatic amines of theformulae (IIa) or (IIb) or cycloaliphatic amines of the formula (IIc)##STR3## in which R⁵, R⁶ and R⁷, independently of each other, are ineach case hydrogen, C₁ -C₄₀ -alkyl, preferably C₁ -C₂₀ -alkyl, C₃ -C₈-cycloalkyl, preferably C₅ -C₆ -cycloalkyl or CY¹ Y² -aryl, where Y¹ andY² independently of each other, are C₁ -C₄ -alkyl, aryl or hydrogen, andaryl is preferably substituted or unsubstituted phenyl, in particularphenyl, aminophenyl, hydroxyphenyl, tolyl, xylyl, nitrophenyl andhalophenyl,

R⁸, R⁹, R¹⁰, R¹¹ and R¹², in each case independently of each other, arehydrogen, C₁ -C₂₀ -alkyl or C₃ -C₈ -cycloalkyl, preferably hydrogen orC₁ -C₃ -alkyl, where R¹² can additionally have the meaning of --(CR¹³R¹⁴)_(p) --,

R¹³ and R¹⁴, independently of each other, are hydrogen or methyl,

m is an integer from 1 to 5, preferably 1 to 2,

n is an integer from 2 to 10, preferably 2 to 3,

p is an integer from 1 to 8, preferably 1 to 6, and

q is an integer from 1 to 5, preferably 1 to 4.

Bases which are additionally preferred in the sense of the presentinvention are alkali metal carbonates, alkaline earth metal carbonates,alkali metal hydrogen carbonates, alkali metal hydrogen phosphates,alkaline earth metal hydrogen phosphates, alkali metal alcoholates,alkaline earth metal alcoholates, alkali metal hydroxides or alkalineearth metal hydroxides, where alkali metal is preferably lithium, sodiumor potassium, and alkaline earth metal is preferably magnesium orcalcium, or a mixture of at least two of the abovementioned bases.

For the purposes of the present invention, the amines which arepreferably selected are those whose boiling points are high enough toensure that they remain at the bottom during a distillation, althoughthis is not absolutely necessary. Low-boiling amines can also besubsequently metered in as required, or continuously, where appropriate.

Examples of the amines of the formula (IIa) which are employed accordingto the invention are: Diethylamine, triethylamine, ethanolamine,diethanolamine, triethanolamine, n- or iso-propylamine, di-n- ordi-iso-propylamine, tri-n- or tri-iso-propylamine, n-, iso- ortert-butylamine, amylamine, hexylamine, cyclohexylamine,dicyclohexylamine, stearylamine, oleylamine, tallow fatty amine, coconutalkylamine, distearylamine, dimethylstearylamine anddimethylbenzylamine.

Examples of the amines of the formula (IIb) which are employed accordingto the invention are: Ethylenediamine, propylenediamine,diethylenetriamine, dipropylenetramine, triethylenetetramine,tripropylene-tetramine, 1,4-diaminobutane, 1,5-diaminopentane and1,6-diaminohexane.

Examples of the amines of the formula (IIc) which are employed accordingto the invention are: Pyrrolidine, piperidine, piperazine,hexahydro-s-triazine, hexamethylenetetramine, hexamethylenimine ortrimethyleneimine.

A mixture of at least two of the abovementioned amines may also beemployed.

Those of the above-described alkali metal compounds and alkaline earthmetal compounds which are in particular employed according to theinvention are: Sodium hydrogen carbonate, sodium carbonate, potassiumcarbonate, disodium hydrogen phosphate, dipotassium hydrogen phosphate,calcium hydroxide, sodium hydroxide, potassium hydroxide, sodiumethanolate, potassium ethanolate, sodium methanolate, potassiummethanolate, sodium propanolate, or a mixture of these bases.

According to the invention, the bases are employed in quantities of 0.01to 10% by weight, preferably 0.1 to 2% by weight, based on theaminobenzotrifluoride. Quantities of the said bases above 10% by weightare likewise suitable for stabilizing the aminobenzotrifluorides, butare no longer expedient from the ecological point of view, and forreasons of economy.

Examples of aminobenzotrifluorides of the formula (I) which are ofinterest are: ##STR4## 2-Aminobenzotrifluoride, 4-aminobenzotrifluorideand 2-amino-5-chloro-benzotrifluoride are of particular industrialinterest.

The present invention furthermore relates to a process for stabilizingaminobenzotrifluorides of the formula (I) defined above, wherein atleast one of the above-mentioned bases is added to theaminobenzotrifluoride, preferably before or during a thermal stress, forexample a distillation. During a thermal stress, the bases can also beadded continuously, or in portions as required. In addition, the basescan be added to the crude or purified aminobenzotrifluoride in order toincrease the storage stability.

The stabilizing influence of the said bases on theaminobenzotrifluorides is very high. For example, with the addition of0.5% by weight of a base, 2-aminobenzotrifluoride can be heated at 150°to 160° C. for several days without decomposition or resinificationtaking place. No decomposition products can be observed bygas-chromatographic analysis. With the addition of a base,4-aminobenzotrifluoride remains stable at 150° C. for 5 hours, whilewithout addition it resinifies after only 1.5 hours at 120° C. Aminesare particularly suitable for increasing storage stability at moreelevated temperatures. The amines dissolve in theaminobenzotrifluorides, so that continuous stirring or circulation ofthe mixture is unnecessary.

If 2-aminobenzotrifluoride is distilled over the above-mentioned bases,the distillate is then more stable than distillates obtained withoutbase addition.

The present invention also relates therefore to the use of theabovementioned bases for increasing the storage stability as well as thethermal stability of aminobenzotrifluorides of the formula (I).

The examples below illustrate the process according to the inventionwithout limiting it thereto.

EXAMPLES 1) Thermal stability of 2-aminobenzotrifluoride (comparativeexample)

10.0 g (62.1 mmol) of 2-aminobenzotrifluoride were heated at 150° C.under a nitrogen atmosphere. After about 1.5 hours, it was observed thatthe starting material was becoming yellow and viscous, and after about 2hours it was completely resinified and solidified. As well as smallquantities of starting material, it was possible to detect, by means ofGC, GC-MS and MS analyses, about 40% of volatile components with weightsgreater than 700 g/mol, as well as non-volatile components with highmolecular weights, in the resin which had formed.

2) Thermal stability of 4-aminobenzotrifluoride (comparative example)

5.0 g (31 mmol) of 4-aminobenzotrifluoride were heated at 120° C. undera nitrogen atmosphere. After about 1.5 hours, the starting material hadcompletely resinified.

3) Thermal stability of 2-amino-5-chlorobenzotrifluoride (comparativeexample)

10.0 g (51.2 mmol) of 2-amino-5-chlorobenzotrifluoride were heated at180° C. under a nitrogen atmosphere. After about 3 hours, the startingmaterial had completely resinified.

The following examples 4 to 21 were carried out with the same resultwith and without blanketing with nitrogen.

4) Thermal stability of 2-aminobenzotrifluoride following the additionof NaHCO₃

25.0 g (155 mmol) of 2-aminobenzotrifluoride were heated at 150° C. for56 hours with 0.5 g of NaHCO₃ having been added. No resinification wasobserved. No decomposition products were detectable by means of GC.

5) Thermal stability of 2-amino-5-chlorobenzotrifluoride following theaddition of NaHCO₃

25.0 g (128 mmol) of 2-amino-5-chlorobenzotrifluoride were heated at150° C. for 56 hours with 0.5 g of NaHCO₃ having been added. Noresinification was observed. No decomposition products were detectableby means of GC.

Examples 6 to 18:

Thermal stability of 2-aminobenzotrifluoride following the addition ofvarious bases

The Examples 6 to 18 listed in the following table were carried out inan analogous manner to Example 4 using in each case 100 g (0.62 mol) of2-aminobenzotrifluoride, and heating at a temperature of 150° C. for 8hours in each case.

    ______________________________________                                        Example       Base                                                            ______________________________________                                        6             0.5 g of NaHCO.sub.3                                            7             0.5 g of Na.sub.2 CO.sub.3                                      8             0.5 g of NaOH (solid)                                           9             0.5 g of Na.sub.2 HPO.sub.4                                     10            0.5 g of Ca(OH).sub.2                                           11            0.5 g of stearylamine                                           12            0.5 g of dimethylbenzylamine                                    13            0.5 g of triethylamine                                          14            0.5 g of cyclohexylamine                                        15            0.5 g of hexamethylenetetramine                                 16            0.5 g of dimethylstearylamine                                   17            0.5 g of sodium methanolate                                     18            0.5 g of distearylamine                                         ______________________________________                                    

The 2-aminobenzotrifluoride remained stable in all the listed examples.No resinification or decomposition was observed.

19) Thermal stability of 4-aminobenzotrifluoride following the additionof stearylamine

10.0 g (62.1 mmol) of 4-aminobenzotrifluoride were heated at 150° C.with 0.5 g of stearylamine having been added. The4-aminobenzotrifluoride remained stable for 5 hours.

20) Thermal stability of 2-amino-5-chlorobenzotrifluoride following theaddition of stearylamine

100 g (0.52 mol) of 2-amino-5-chlorobenzotrifluoride were heated at 185°C. with 0.5 g of stearylamine having been added. The2-amino-5-chlorobenzotrifluoride remained stable for 8 hours. Nodecomposition or resinification was observed.

21) Thermal stability of 4-aminobenzotrifluoride following the additionof NaHCO₃

10.0 g (62.1 mmol) of 4-aminobenzotrifluoride were heated at 150° C.with 0.5 g of NaHCO₃ having been added. The 4-aminobenzotrifluorideremained stable for 5 hours.

22) Distillation of 2-aminobenzotrifluoride with stearylamine havingbeen added

100.0 g (621 mmol) of 2-aminobenzotrifluoride were mixed with 0.5 g ofstearylamine and distilled at 80° C./0.04 bar through a 20 cm Vigreuxcolumn. The distillate thus obtained is heated at 150° C. Only after 6hours were there signs of an incipient resinification; after about 7.5hours the preparation had completely resinified.

We claim:
 1. A stabilized aminobenzotrifluoride, composition consistingessentially ofa) an aminobenzotrifluoride of the formula (I), ##STR5##in which R¹ and R², independently of each other, are hydrogen, C₁ -C₆-alkyl, C₂ -C₆ -alkenyl, substituted or unsubstituted aryl, halogen,CF₃, nitro, amino, methoxy, hydroxyl or NR³ R⁴, where R³ and R⁴independently of each other, are hydrogen or C₁ -C₅ -alkyl radicals, andthe NH₂ group can be located in the 2-, 3- or 4-position in relation tothe CF₃ group, and b) at least one base.
 2. The composition as claimedin claim 1, wherein, in the aminobenzotrifluoride of the formula (I), R¹and R², independently of each other, are in each case hydrogen, C₁ -C₄-alkyl, C₂ -C₄ -alkenyl, fluorine, chlorine, bromine, CF₃, NO₂, NH₂,OCH₃, OH, substituted or unsubstituted phenyl, or NR³ R⁴, in which R³and R⁴, independently of each other, are hydrogen or C₁ -C₃ -alkyl. 3.The composition as claimed in claim 1, wherein, in theaminobenzotrifluoride of the formula (I), R¹ and R² independently ofeach other, are in each case hydrogen, methyl, C₂ -C₄ -alkenyl,fluorine, chlorine, bromine, CF₃, NO₂, NH₂, OCH₃, OH, phenyl,hydroxyphenyl, tolyl, xylyl, aminophenyl, halophenyl, nitrophenyl or NR³R⁴, in which R³ and R⁴, independently of each other, are hydrogen or C₁-C₃ -alkyl.
 4. The composition as claimed in claim 1, wherein theaminobenzotrifluoride is 2-aminobenzotrifluoride,3-aminobenzotrifluoride, 4-aminobenzotrifluoride,2-amino-5-chlorobenzotrifluoride, 3-amino-4-nitrobenzotrifluoride,2,5-diamino-4-trifluoromethylbenzotrifluoride,3-amino-2-methylbenzotrifluoride or a diaminobenzotrifluoride.
 5. Thecomposition as claimed in claim 1, wherein the base is a primary,secondary or tertiary amine of the formulae (IIa) or (IIb) or acycloaliphatic amine of the formula (IIc) ##STR6## in which R⁵, R⁶ andR⁷, independently of each other, are in each case hydrogen, C₁ -C₄₀-alkyl, C₃ -C₈ -cycloalkyl, or CY¹ Y² -aryl, where Y¹ and Y₂,independently of each other, are C₁ -C₄ -alkyl, aryl or hydrogen, andaryl is substituted or unsubstituted phenyl,R⁸, R⁹, R¹⁰, R¹¹ and R¹², ineach case independently of each other, are hydrogen, C₁ -C₂₀ -alkyl orC₃ -C₈ -cycloalkyl, where R¹² can additionally have the meaning of--(CR¹³ R¹⁴)_(p) --, R¹³ and R¹⁴ independently of each other, arehydrogen or methyl, m is an integer from 1 to 5, n is an integer from 2to 10, p is an integer from 1 to 8, and q is an integer from 1 to 5,oris a mixture of the abovementioned amines.
 6. The composition as claimedin claim 1, wherein the base is a primary, secondary or tertiary amineof the formulae (IIa) or (IIb) or a cycloaliphatic amine of the formula(IIc) ##STR7## in which R⁵, R⁶ and R⁷ independently of each other are ineach case hydrogen C₁ -C₂₀ -alkyl, C₅ -C₆ -cycloalkyl or CY¹ Y² -aryl,where Y¹ and Y², independently of each other, are C₁ -C₄ -alkyl, aryl orhydrogen, and aryl is phenyl, aminophenyl, hydroxyphenyl, tolyl, xylyl,nitrophenyl or halophenyl,R⁸, R⁹, R¹⁰, R¹¹ and R¹², in each caseindependently of each other, are hydrogen or C₁ -C₃ -alkyl, where R¹²can additionally have the meaning of --(CR¹³ R¹⁴)_(p) --, R¹³ and R¹⁴,independently of each other, are hydrogen or methyl, m is an integerfrom 1 to 2, n is an integer from 2 to 3, p is an integer from 1 to 6,and q is an integer from 1 to 4,or is a mixture of the abovementionedamines.
 7. The composition as claimed in claim 1, wherein the base isstearylamine, diethylamine, triethylamine, cyclohexylamine,dimethylbenzylamine, ethanolamine, diethanolamine, triethanolamine, n-or iso-propylamine, di-n- or di-iso-propylamine, tri-n- ortri-iso-propylamine, n-, iso- or tert-butylamine, amylamine, hexylamine,cyclohexylamine, oleylamine, tallow fatty amine, coconut alkylamine,distearylamine, dimethylstearylamine, dimethylbenzylamine,ethylenediamine, propylenediamine, diethylenetriamine,dipropylenetriamine, triethylenetetramine, tripropylenetetramine,1,4-diaminobutane, 1,5-diaminopentane, 1,6diaminohexane, pyrrolidine,piperidine, piperazine, hexahydro-s-triazine, hexamethylenetetramine,hexamethyleneimine, trimethyleneimine, or a mixture of at least two ofthe said amines.
 8. The composition as claimed in claim 1, wherein thebase is stearylamine, triethylamine, cyclohexylamine,dimethylstearylamine, distearylamine, hexamethylenetetramine, or amixture of at least two of the said amines.
 9. The composition asclaimed in claim 1, wherein the base is an alkali metal carbonate,alkaline earth metal carbonate, alkali metal hydrogen carbonate, alkalimetal hydrogen phosphate, alkaline earth metal hydrogen phosphate,alkali metal alcoholate, alkaline earth metal alcoholate, alkali metalhydroxide or alkaline earth metal hydroxide, where alkali metal islithium, sodium or potassium and alkaline earth metal is magnesium orcalcium, or a mixture of the abovementioned bases.
 10. The compositionas claimed in claim 9, wherein the base is sodium hydrogen carbonate,sodium carbonate, sodium hydroxide, sodium methanolate, disodiumhydrogen phosphate, calcium hydroxide, or a mixture of at least two ofthe said bases.
 11. The composition as claimed in claim 1, wherein saidcomposition contains the base in a quantity of 0.01 to 10% by weight,based on the aminobenzotrifluoride.
 12. The composition as claimed inclaim 1, wherein said composition contains the base in a quantity of 0.1to 2% by weight, based on the aminobenzotrifluoride.
 13. A process forstabilizing aminobenzotrifluorides of the formula (I) as claimed inclaim 1, wherein at least one base is added to theaminobenzotrifluoride.
 14. The process as claimed in claim 13, whereinthe base is added to the aminobenzotrifluoride before or during athermal stress.
 15. A method of increasing the storage stability and thethermal stability of aminobenzotrifluorides of the formula (I) ##STR8##in which R¹ and R² independently of each other, are hydrogen, C₁ -C₆-alkyl, C₂ -C₆ -alkenyl, substituted or unsubstituted aryl, halogen,CF₃, nitro, amino, methoxy, hydroxyl, or NR³ R⁴, where R³ and R⁴,independent of each other are hydrogen or C₁ -C₅ -alkyl radicals, andthe NH₂ group can be located in the 2-, 3-, or 4-position in relation tothe CF₃ group, comprising the step ofadding a base to saidaminobenzotrifluoride, said base comprising a primary, secondary, ortertiary amine of the formulae (IIa) or (IIb) or a cycloaliphatic amineof the formula (IIc) ##STR9## in which R⁵, R⁶, and R⁷, independently ofeach other, are in each case hydrogen, C₁ -C₂₀ -alkyl, C₅ -C₆-cycloalkyl or CY¹ Y² -aryl, where Y¹ and Y² independently of eachother, are C₁ -C₄ -alkyl, aryl, or hydrogen, and aryl is phenyl,aminophenyl, hydroxyphenyl, tolyl, xylyl, nitrophenyl or halophenyl, R⁸,R⁹, R¹⁰, R¹¹, R¹², in each case independently of each other, arehydrogen or C₁ -C₃ -alkyl, where R¹² can additionally have the meaningof --(CR¹³ R¹⁴)_(p) --, R¹³ and ¹⁴, independently of each other, arehydrogen or methyl, m is an integer from 1 to 2, n is an integer from 2to 3, p is an integer from 1 to 6, and q is an integer from 1 to 4.